Maybe to knock the piercing modifier down to 1.0, instead of whatever it is currently. Even flamethrowers deal damage to chem sprayed parts. Just not much. Similarly, this would remove the extra effectiveness of piercing weapons, while not eliminating the damage entirely. Also, probably drop it to 10 seconds duration tops, so you have to really stay on top of it.
This would probably break the game, and make triple artemis *the* weapon choice of the future. Something that didn't depend on piercing.